Vaccine strategies to achieve effective immunity to pathogens must establish short-lived effector and a reserve of long-lived memory T cells. Mycobacterium tuberculosis and Schistosoma mansoni represent epidemic pathogens for which vaccine development has been difficult to achieve. These pathogens evoke T helper (Th) cell-mediated, mononuclear cell-rich, sequestration responses known as granulomas (GR). The role of CD4+ Th cells in the GR response to these pathogens is well established. Moreover, mycobacterial and schistosomal antigens, respectively elicit polarized Th1 (type-1) and Th2 (type-2) hypersensitivity-type GR formation. We have examined the role of chemoattractant proteins in these responses. Our objective was to identify critical chemokines and chemokine receptors required for effective and appropriate responses to these pathogens. We identified CC-chemokine receptor 4 (CCR4) as a T and dendritic cell-expressed chemokine receptor that participates in the GR response, with particular relevance to the mycobacterial response. Initial analyses suggested that CCR4 mediates interactions with antigen presenting dendritic cells (DCs) to promote survival or maturation of Th effector/memory cells. The studies proposed herein will test the hypothesis that pathogenelicited CD4+ Th1 and Th2 cells have different chemokine requirements for sustenance of effector and central memory function. Specifically, CD4+ Th1 effector and central memory responses to mycobacteria require CCR4-mediated interactions with antigen presenting myeloid dendritic cells (mDCs). In contrast, Th2 effectors may utilize CCR4 for tissue mobilization, but Th2 central memory is sustained through alternative antigen presenting cells. This hypothesis will be tested under conditions of Mycobacterium bovis and Schistosoma mansoni exposure by way of the following aims. Aim 1 will define the role of CCR4 in the development of innate effector responses. Aim 2 will determine the contribution of T cell CCR4 expression to the generation and mobilization of short-lived effector memory CD4+ Th cells. Aim 3 will assess the contribution of T cell CCR4 expression to the maintenance and elicitation of central memory CD4+ Th cells. Aim 4 will determine the contribution of myeloid dendritic cell (mDC) CCR4 expression to the generation and sustenance of effector and central memory CD4+ Th responses. Aim 5 will determine the contribution of CCR4 to mDC maturation, function and localization. Methodologies will include the use of CCR4 targeted knockout mice, recombinant ovalbumin-producing M. bovis BCG-strain (BCG-OVA), adoptive D10.11 transgenic T cell transfer, preparation of bone marrow chimeras, mDC preparation and culture, gene expression analysis, and flow cytometry. Mycobacterial and helminth infections are responsible for a profound degree of global morbidity and mortality. The studies proposed herein will help the design of improved approaches to vaccine development and therapies to control chronic destructive inflammatory responses.